1.由81³×27^4=x^6
81³×81³=x^6
81^6=x^6,
∴x=81
(27^4=9^6=81³)
2.由2^n=8,∴n=3,
3^m=9,∴m=2,
(2^3n+2^m)³
=(2^9+2²)³
=(512+4)³
=516³
3.由（a-2)^4+|2b-1|=0
∴a-2=0,即a=2,
2b-1=0,即b=1/2
a^2005×b^2005
=(ab)^2005
=1.
4.(2x^3n)²-3(x^n)^4
=4x^6n-3x^4n
∵x^2n=5,∴x^4n=25,x^6n=125
代入：4×125-3×25
=500-75
=425.这些是啥？看不懂不要紧，仔细看，可以看懂的。读八年级？